Imaging apparatus comprising a ring-shaped gantry

ABSTRACT

An imaging apparatus comprising a ring-shaped gantry is provided. The gantry has a rotor arrangement rotating therein and a radiation source as well as at least one radiation detector. The gantry has at least one gantry segment which can be detached from the ring shape to allow the gantry to be opened laterally. The gantry is arranged on a supporting structure so as to be movable in space. The supporting structure is a floor, wall or ceiling mounted articulated-arm robot having at least four, preferably six, degrees of freedom of movement. The gantry has at least two radiation sources disposed offset by an angle on the rotor arrangement and associated with each of which is at least one radiation detector.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority of German application No. 10 2010 020603.2 filed May 14, 2010, which is incorporated by reference herein inits entirety.

FIELD OF THE INVENTION

The invention relates to an imaging apparatus comprising a ring-shapedgantry having a rotor arrangement rotating therein and having an imageacquisition means comprising a radiation source as well as at least oneradiation detector, wherein the gantry having at least one gantrysegment which can be detached from the ring shape to allow the gantry tobe opened laterally is arranged on a supporting structure so as to bemovable in space.

BACKGROUND OF THE INVENTION

Minimally invasive interventions and minimally surgical interventionalprocedures on patients are increasingly replacing traditional surgicaloperations. A factor of crucial importance in this regard is goodanatomical and functional medical imaging, in particular of soft tissue,in the case of interventions involving the heart and liver for example.For this purpose use is predominantly made of X-ray devices foracquiring fluoroscopic images, said devices possessing a certainmobility to enable the image acquisition means to be positioned asappropriate in order to permit the intervention that is being performedin parallel. Mobile C-arm X-ray machines are known in which a radiationsource and a radiation detector are arranged at the ends of a C-arm,said C-arm having the ability to be moved in space and positionedrelative to the patient or, as the case may be, the treatment region.However, X-ray machines of this kind generally provide only 2D imagesand sometimes the soft-tissue resolution is unsatisfactory or the imagequality is not such that sufficient information can be acquired inparticular in the case of complex interventions.

Improved image acquisition, including with regard to three-dimensionalimaging, is possible by means of an imaging apparatus comprising aring-shaped gantry, i.e. a mobile computed tomography (CT) scanner or amobile computed tomography gantry which is arranged on a supportingstructure such as a mobile cart which can travel across a floor forexample, as described by way of example in U.S. Pat. No. 6,940,941. Bymeans of such a mobile CT scanner, in the gantry of which there rotatesa rotating rotor arrangement having an image acquisition meanscomprising a radiation source and, for example, a radiation detectorarranged offset by 180° therefrom, i.e. disposed opposite thereto,images can be recorded continuously during the treatment owing to thecontinuous rotation of the rotor arrangement, thereby resulting in verygood soft-tissue resolution within the acquired images, and consequentlyin very good image quality. Also provided in the case of the gantryknown from U.S. Pat. No. 6,940,941 is a detachable or breakable gantrysegment, which is to say that the gantry can be opened laterally, thusenabling the patient to be introduced into the gantry from the lateraldirection.

However, a disadvantage of the known mobile gantry is to be seen in thefact that e.g. the mobile cart on which the gantry is arranged takes upa considerable amount of space which is then no longer available forpositioning other equipment required for a treatment or in which it isalso not possible for persons involved in the treatment to remain.

In particular in computed tomography examinations of the heart it isfurthermore only possible to record an entire cardiac cycle using animage acquisition means having a rotating radiation source when theheart rate is reduced to 60 bpm or less with the aid of suitable drugs,beta blockers for example. This is disadvantageous for the patient onthe one hand, and on the other hand optimal image acquisition is notalways assured, especially at somewhat slower rotational speeds.

SUMMARY OF THE INVENTION

The problem underlying the invention is therefore to improve an imagingapparatus of the type cited in the introduction in terms of itsaccessibility and also in terms of the quality of the imaging.

In order to solve this problem it is provided according to the inventionin the case of an imaging apparatus of the type cited in theintroduction that the supporting structure is a floor-, wall- orceiling-mounted articulated-arm robot having at least four, preferablysix, degrees of freedom of movement, wherein there are provided in thegantry at least two radiation sources disposed offset by an angle on therotor arrangement and associated with each of which is at least oneradiation detector.

According to the invention the openable gantry is arranged on anarticulated-arm robot secured to the floor, wall or ceiling, i.e. it isguided from below, from the side or from above. A transport cart that ismovable across the floor or a similar contrivance is no longer providedaccording to the invention, thereby consequently considerably improvingthe accessibility of the gantry both with regard to the positioning ofany equipment and for people as well as with regard to the possibilityof easily positioning the patient.

The gantry is also characterized by the use of two radiation sourceswhich are disposed offset by a defined angle from each other in or onthe rotor arrangement. By means of said two radiation sources inconjunction with the associated detectors it is possible to recordimages at twice as high a heart rate or, as the case may be, to record acomplete cardiac cycle in full even at the normal heart rate. Towardthat end the two radiation sources are operated in parallel, thedetectors continuously providing parallel images, though from differentprojection directions. As a result of this it is no longer absolutelynecessary to administer any drugs to slow the heart rate on the onehand, while on the other hand high-quality images of a moving organ canbe recorded even at somewhat lower rotational speeds.

In order to enable adequate freedom of movement and as a result thereofpositioning freedom of the gantry it is already sufficient if thearticulated-arm robot has at least four degrees of freedom of movement,with preferably five or in particular six degrees of freedom beingprovided. A further improvement in the freedom of movement or, as thecase may be, positioning capability is given if the articulated-armrobot is mounted on the floor, wall or ceiling so as to be movable alongat least one, preferably two horizontal or vertical axes standingperpendicularly relative to one another. By this means the entirearrangement consisting of robot and gantry can additionally be varied interms of its space coordinates, thus further increasing the positioningfreedom. The movement of the robot, whether it be its arms around thecorresponding revolute joints themselves, whether it be the entire robotalong the linear rail guides on the floor, wall or ceiling, ispreferably effected by means of suitable motors which are arranged atthe corresponding movement interfaces or engage there. To control themovement a suitable control device is provided via which all of themotors are controlled, for example using a joystick or a similar controlelement.

As described, at least one radiation detector is associated with each ofthe two radiation sources. This can be implemented in such a way thattwo radiation detectors are also disposed on the rotor arrangement inaddition to the two radiation sources and co-rotate with said rotorarrangement. The detectors are disposed opposite the respectiveradiation sources, in other words are positioned offset by 180°. Thus,two radiation source-radiation detector pairs are folioed. Alternativelythe assignment of the detectors can also be realized in such a way thata multiplicity of detectors are arranged in a stationary manner on thegantry, the detectors complementing one another to form a ring shape. Inthis case, therefore, the two radiation sources rotate relative to thepositionally fixed radiation detectors such that each radiation sourceis associated with a multiplicity of detectors, ultimately with all ofthe detectors integrated in the detector ring.

Typical detectors used in the case of a computed tomography scanner arecomposed of a plurality of individual detectors. They possess goodtemporal resolution, though at a pixel size of approx. 400 μm sometimeshave only a limited spatial resolution. Whereas two radiation sourcesare provided in the imaging apparatus according to the invention, it isprovided according to a particularly advantageous development of theinvention to use radiation detectors of different types, wherein oneradiation detector is a known, conventional CT receiver consisting of amultiplicity of individual detectors and the other radiation detector isa planar solid-state radiation detector. Such a solid-state radiationdetector possesses a considerably smaller pixel size of, for example,approx. 100 μm and hence a good spatial resolution, albeit a somewhatpoorer temporal resolution. If two different radiation detectors are nowused, the advantages of the respective receiver types can be exploitedand at the same time the respective disadvantages compensated for. Thesolid-state radiation detector can be, for example, a detector based onamorphous silicon (aSi), a CMOS detector, a detector based on cadmiumtelluride (CdTe) or cadmium zinc telluride (CzT) or a detector based onorganic photodiodes.

One radiation source is preferably a carbon nanotube emitter.

The rotor arrangement itself preferably extends through an angle of max.270°, which is to say that the gantry can be opened with a segmentdescribing at least 90°, although opening over a quadrant is alsogenerally sufficient for positioning the patient.

In this case the rotor arrangement itself is embodied in such a wayand/or the image acquisition means are disposed on the rotor arrangementin such a way that the two radiation sources are arranged offset by 90°from each other. The result of this, insofar as the detectors aredisposed on the rotor arrangement, is that the detectors are likewisearranged offset by 90° from each other; overall, all elements of theimage acquisition means are spaced 90° apart from one another. At thesame time the rotor arrangement itself can extend through 270° and aradiation source or a radiation detector can be positioned at its ends.It is, however, also conceivable that the rotor arrangement extendsthrough a smaller angle and the radiation source or the radiationdetector is positioned so as to effectively lengthen the rotorarrangement. In any event a gantry segment extending through max. 90°can still be opened as before.

Furthermore a patient positioning table can be provided which can bemoved translationally and/or rotationally in space. It can be adjustedmanually or in a motor-driven manner in terms of its height, length andtransverse direction, and can be fixed to the floor, wall or ceiling byway of a suitable supporting structure. An optional inclination in thex-, y- and/or z-direction is also possible, while the patientpositioning table can also optionally rotate about a central point; acircular or elliptical rotational movement about a fixed point is alsoconceivable. In particular the use of an articulated-arm robot having atleast four, preferably six, degrees of freedom is suitable for movingthe patient positioning table, said articulated-arm robot, in particularif having six degrees of freedom, enabling translational and rotationalmovements in or about any spatial direction axis and consequentlyallowing an arbitrary positioning of the patient positioning table inspace.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages, features and details of the invention will emergefrom the exemplary embodiment described below as well as with referenceto the drawings, in which:

FIG. 1 is a schematic representation of an imaging apparatus accordingto the invention with closed gantry,

FIG. 2 shows the imaging apparatus from FIG. 1 with open gantry,

FIG. 3 is a schematic representation of a gantry having two rotatingradiation sources and a multiplicity of stationary radiation detectors,and

FIG. 4 is a schematic representation of a gantry having three rotatingradiation sources and a multiplicity of stationary radiation detectors.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows in the form of a schematic diagram an imaging apparatus 1according to the invention, comprising a gantry 2 which is arranged on aceiling 4 so as to be movable by way of an articulated-arm robot 3. Thegantry 2 comprises a rotor arrangement 5 which, driven by way of amotor, rotates about the center point M on runner rails (not shown infurther detail) located inside the gantry 2. The rotor arrangement 5extends through approx. 270°. This enables it to be brought into a parkposition in which a segment 6 of the gantry which is pivotably mountedby way of a hinge 7 can be swung open (see FIG. 2) so that the inside ofthe gantry 2 is accessible. It is now possible to position a patient(not shown in further detail) inside the gantry 2 by means of a patientpositioning table 8 on which the patient is located and which in theexample shown can be moved in space by way of a cart 9. Appropriatelocking means (not shown in further detail) are of course provided forthe purpose of fixing the rotor arrangement in position as well as forlocking the segment 6 of the gantry 2.

In the example shown the rotor arrangement 5 carries two radiationsources 10, 11 which are X-ray tubes, preferably carbon nanotubeemitters. The two radiation sources 10, 11 are spaced apart from eachother by 90°. Disposed opposite each radiation source 10, 11 is aradiation detector 12, 13, these likewise being arranged spaced apart by90° from the respective radiation source. In other words all fourcomponents are therefore spaced apart from one another by 90°. In thisembodiment the radiation detectors 12, 13 co-rotate with the radiationsources 10, 11, i.e. two pairs made up of a radiation source and aradiation detector are faulted, namely the pair 10-12 and the pair11-13. The radiation detectors 12, 13 can be of the same type, althoughpreferably they are of different types. While the radiation detector 12can be a conventional computed tomography detector consisting of amultiplicity of individual detectors arranged adjacent to one another,the radiation detector 13 can be for example a planar solid-stateradiation detector based for example on aSi or similar.

The articulated-arm robot 3 itself is arranged on ceiling rails 14 andcan be moved in at least one horizontal direction, as indicated by thedouble arrow P1. It is of course possible to realize an additionalmovability in a horizontal direction at right angles thereto, for whichpurpose a further movement plane would need to be provided.

Furthermore, the arms 16 a, 16 b, 16 c of the articulated-arm robot 3can be rotated about its multiple revolute joints 15 a, 15 b, 15 c, eachrevolute joint 15 a, 15 b, 15 c possessing two degrees of rotationalfreedom, as indicated by the respective double arrows P2 a, P2 b, Pia,P3 b and P4 a, P4 b. This enables the gantry 2 mounted on the arm 16 cto be positioned arbitrarily in space. In conjunction with theceiling-side movability of the entire arrangement, a virtually arbitrarypositioning capability of the gantry 2 in space is realized by thismeans.

When a patient is to be examined the gantry 2 is first moved into thedesired position in which it is possible to introduce the patient intothe gantry. This is preferably accomplished automatically in thatsuitable motors are provided at the respective movement interfaces ofthe articulated-arm robot 3 or its revolute joint 16 a, 16 b, 16 c forthe purpose of effecting the respective movement. This is controlled bythe user by way of a central control device (not shown in furtherdetail) for example with the aid of a joystick or similar. A hydraulicor pneumatic movement in the respective planes/axes would also beconceivable instead of a motorized movement.

After the transfer position has been reached a check is first made todetermine whether the rotor arrangement 5 is in the rest or parkposition in order then, after locking the rotor arrangement 5 andopening the segment lock, to open the segment 6 of the gantry 2 andintroduce the patient by way of the patient positioning table 8. Afterthe patient has been positioned the segment 6 is then closed again,whereupon the examination can begin, in the course of which the rotorarrangement 5 rotates at high speed around the center M of the gantry 2.In the process both radiation sources 10, 11 are operatedsimultaneously, while images are also simultaneously and continuouslyrecorded from the different fluoroscopic directions via both radiationdetectors 12, 13, said images subsequently being processed in thecontrol device (not shown in further detail), analyzed and displayed ona monitor.

FIGS. 3 and 4 show in a schematic representation two further embodimentvariants of a gantry 2 which again has a segment 6 which is pivotablymounted by way of a hinge 7 and allows the gantry 2 to be opened. Atthis point it should be noted that other movement mechanisms can, ofcourse, also be provided for releasing the segment 6 from its ringposition. For example, it can be removed completely by way of a suitableremoval mechanism, while lifting it on a linear bearing and similar isalso conceivable.

Here too a rotor arrangement 5 is provided which carries both radiationsources 10, 11, though not the radiation detectors, for which reason therotor arrangement 5 in the example shown also only extends throughsomewhat more than 90°. The two radiation sources 10, 11 are spacedapart from each other by 90°. In this case also the rotor arrangement 5runs on suitable guide rails (not shown in further detail) of the gantry2, while a motor (likewise not shown in further detail) is in turnprovided as a driving means.

In contrast to the embodiments according to FIGS. 1 and 2, in this casea multiplicity of individual stationary radiation detectors 12 areprovided which are arranged fixed in position on the gantry 2 and can beimpinged upon by X-ray radiation from the respective radiation sources10, 11. The radiation detectors 12 complement one another to create aring shape, thus fondling a complete, closed detector ring. It ispossible to arrange radiation detectors of different types in twosuccessive planes, i.e. one detector ring consisting of radiationdetectors 12 in a first plane, for example, and a radiation detectorring consisting of radiation detectors 13 in a second, immediatelycontiguous plane, so that the advantageous properties of the differentdetector types can be used in this case too.

Finally, FIG. 4 shows an embodiment variant having three radiationsources 10, 11, 17 which are again arranged on a common rotorarrangement 5 which in turn extends through less than 270° around theinner circumference of the gantry 2. Here too stationary radiationdetectors 12 or 13 arranged in a ring shape are again provided in one ortwo planes.

The invention claimed is:
 1. An imaging apparatus, comprising: asupporting structure movable in space; and a ring-shaped gantry arrangedon the supporting structure comprising: a rotor arrangement rotating inthe gantry, at least two radiation sources disposed offset by an angleon the rotor arrangement, and at least two radiation detectors eachassociated with each of the radiation sources, wherein the gantrycomprises a gantry segment that can be detached from the gantry to allowthe gantry to be opened laterally, and wherein the supporting structureis an articulated-arm robot having at least four degrees of freedom ofmovement.
 2. The imaging apparatus as claimed in claim 1, wherein thearticulated-arm robot has six degrees of freedom of movement.
 3. Theimaging apparatus as claimed in claim 1, wherein the articulated-armrobot is mounted on a floor, a wall or a ceiling to be movable along atleast one horizontal or vertical axes standing perpendicularly relativeto one another.
 4. The imaging apparatus as claimed in claim 1, whereinthe radiation detectors associated with the radiation sources aredisposed opposite the radiation sources on the rotor arrangement.
 5. Theimaging apparatus as claimed in claim 1, wherein a plurality ofstationary radiation detectors complementing one another to form a ringshape is arranged in the gantry.
 6. The imaging apparatus as claimed inclaim 1, wherein the radiation detectors comprise different types. 7.The imaging apparatus as claimed in claim 1, wherein one of theradiation detectors is a receiver consisting of a multiplicity ofindividual detectors and the other radiation detector is a planarsolid-state radiation detector.
 8. The imaging apparatus as claimed inclaim 1, wherein one of the radiation sources is a carbon nanotubeemitter.
 9. The imaging apparatus as claimed in claim 1, wherein therotor arrangement rotates through an angle of maximum 270°.
 10. Theimaging apparatus as claimed in claim 1, wherein the two radiationsources are arranged offset by 90° from each other.
 11. The imagingapparatus as claimed in claim 1, further comprising a patientpositioning table that is movable translationally and/or rotatably inspace.
 12. The imaging apparatus as claimed in claim 11, wherein thepatient positioning table is arranged on a further articulated-arm robothaving at least four, or six degrees of freedom.